I've been spending a bit of time recently with Orcs Must Die. It takes the tired old tower defence genre and refreshes it by using the player character as a mobile defensive platform. The whole game is played from a third person over the shoulder viewpoint. It's not the first game to ever try something like this, but there's something about the satisfying way that the different traps work in synergy with each other and the player character, the the attractive and well designed levels and the superbly balanced game progression that draws me back to it time and time again. Terrorhedron is diametrically opposed to that game in almost all respects. It's a very abstract and simply designed tower defence game played from a movable point in space. I have to admit that I wasn't all that impressed after running through the tutorial and getting stuck in to my first few levels. After all, we've all seen tower defence games before and at first glance Terrorhedron has nothing special to offer - or does it?

I've gone from flipping bloodthirsty orcs off of launching platforms into burning tar pits and finishing them off with a wild swing of my mighty claymore to shooting inanimate polyhedrons with tiny cannons. Terrorhedrons? Not quite sure where the terror comes from – let's just hope that the developers were going for a bit of ironic humour there (in which case I'm still only going to give the title a 5/10). Aside from the groovy 8-bit style chiptunes and the clean geometric 3-D visual style, initial gameplay impressions were not good.

Polyhedrons enter the level through a portal and continue via a predetermined path to an exit. Placed around the levels at pre-determined spots are attachment points that the player can use to create defensive turrets. Once the level starts, the turrets attack the targets and depending on the placement and applied strategy, can destroy all of them. If some polyhedrons make it to the exit portal, the players initial score of one hundred is reduced depending on the enemy's remaining strength. When the players score reaches zero, the game is over. Ho-hum, been there, done that.

After a while though the game does become a lot more engaging. The persistent level up and reward system that the game uses make the game increasingly more interesting the longer the player perseveres with it. At first you are limited to one map and one turret type. As experience points are earned though, many more defensive possibilities are opened up, and new maps are unlocked. There are a half dozen different turrets along with a few levels of upgrade as well as coupling parts that can be used to create monster segments of hot death for any passing enemies. Turrets can be used to slow enemies down, or even disable them for short periods of time and coupling blocks can be used to attack from advantageous positions. Positioning a rail gun turret at the end of a long straight section is, for example, very effective. Even when you are overrun, your unlocks carry through to subsequent games, which is a nice feature. To give an idea of the progression speed through the game, after about four hours of play (including two annoying crash to desktops) I have achieved level sixteen. This allows me five different turret types (with three variations of most of them), three maps, and two different coupling blocks.

Still the game remains somewhat unsatisfying for a number of reasons for me. The first few waves of each map are extremely boring. With only a small amount of cash, only a couple of turrets can be placed. It's simply a matter of picking the spots that have the best coverage, and going off to make a cup of coffee for the first few rounds. As polyhedrons are hit, they change colour and speed in a vaguely predictable manner. Sometimes this results in them speeding up, which doesn't make a lot of sense to me. There is no way to slow down or replay waves, so if you're unlucky and are looking the other way as a few enemies sneak through your defences, there's no way to learn from your mistake. The difficulty level feels ridiculously high. I cannot even clear more than 21 waves on easy mode on any of the maps I have unlocked. The game ships with five difficulty modes, the highest of which is “Mathematically Impossible”. When you're consistently losing over and over again, the game needs to be providing something in return for your time. I accept that my strategy might not be very good. Still, I'm going to argue that many casual players might not ever win a map (assuming that it is possible to win at all) on the easiest difficulty level.

The game advertises co-op as a feature, but other computers on my home network were not able to join created games, even after forwarding port 1337 on my router and making an exception for my firewall. I wouldn't have even known to do that unless I'd visited the game's homepage and searched the forums, there is no documentation at all included in the install package. Most importantly for me, the abstract style of the game leads to an overwhelming indifference to the oncoming polyhedron army. In other words, the game is visually appealing in an aesthetic sense in the same way as Osmos is, for example, but is not particularly evocative in any way. I want to hate those polyhedrons in the same way that I loathe those Orcs that invade my castle in the other game. The art style and graphics are fine; there are some nice effects and everything animates smoothly. It's just that the whole gameworld feels a bit sterile and detached.

There are certain features that I like a lot though. The modular construction that becomes available once enough cash is saved up is quite addictive. Playing with angles and combinations of turrets is a lot of fun. Turrets can be individually programmed to prioritise targets based on different parameters. Coupled with the above-mentioned placement and building mechanics, this allows for a lot of flexibility in creating some customised barrages. Probably, this is when the game is playing at its best. For me, this period is about wave 15 and onwards on each map. Trouble is, the difficulty really ramps up here, and just as a level is starting to get interesting, one or two enemies slip through, and it's game over. Music and sound effects are outstanding. A very intuitive camera control scheme allows the action to be viewed from virtually any perspective. Even if you get yourself a bit lost, a quick tap of the space bar resets the view to a default position. The interface is simple and effective.

For mine, the game suffers because the engaging gameplay is simply too sparse. At it's best, Terrorhedron is one of the better tower defence games out there. But having to unlock everything before it can even be placed, and then having sit through too many levels on each map before you have enough cash to make things interesting is a bit of a chore. I couldn't personally recommend it for those reasons, but if you're a fan of the genre (which to be honest, I'm really not) then it might be worth a play through. At the $10 price-point the game is competing with other indies like Revenge of the Titans, Orcs Must Die and Sanctum, where it will struggle for market share. It's certainly not a bad game by any measure but it doesn't offer enough to keep me wanting to play it.